Typically some 1911 owners will add a mag well extension that has more of a bevel to allow quicker mag changes. An extended mag base fills that extra room making the mag easier to seat fully. Stick to standard bases unless you want to start doing modifications to the gun. Reading rewiews on a site like www.midwayusa.com can help with some of the questions and shows how effective these afermarket mags are on 1911 function. WC or Chip McCormick typically show up in 1911s that need to be reliable.http://forums.1911forum.com/index.php is another excellent resource for 1911 function.
I use Wilson Combat 47D,s on my 4" barreled Kimber, hard to beat the 47D for fit and reliability.
Yes I've got several of the Wilson Elite. No real difference in .45 ACP. I prefer them for 9 mm for the extra round i.e. 10